On-substrate mechanical stress sensing and compensation

Abstract

In described examples, a circuit includes a substrate and a first resistor on the substrate, the first resistor in a first direction. The circuit also includes a second resistor on the substrate, the second resistor coupled to the first resistor, the second resistor in a second direction, the second direction and the first direction transversely oriented and a device on the substrate.

What is claimed is: 
     
         1 . A circuit comprising:
 a substrate;   a first resistor on the substrate, the first resistor in a first direction;   a second resistor on the substrate, the second resistor coupled to the first resistor, the second resistor in a second direction, the second direction and the first direction transversely oriented; and   a device on the substrate.   
     
     
         2 . The circuit of  claim 1 , wherein a portion of the device is adjacent to the first resistor. 
     
     
         3 . The circuit of  claim 1 , wherein the device is located between the first resistor and the second resistor. 
     
     
         4 . The circuit of  claim 1 , further comprising a compensating circuit on the substrate, the compensating circuit coupled to the first resistor and to the second resistor. 
     
     
         5 . The circuit of  claim 1 , wherein the substrate comprises a piezoelectric material. 
     
     
         6 . The circuit of  claim 1 , wherein the first resistor and the second resistor form a first directional stress sensor, the circuit further comprising a second directional stress sensor on the substrate. 
     
     
         7 . The circuit of  claim 1 , further comprising:
 a third resistor on the substrate, the third resistor in the first direction; and   a fourth resistor on the substrate, the fourth resistor in the second direction, the fourth resistor coupled to the third resistor.   
     
     
         8 . The circuit of  claim 7 , wherein the device is between the first resistor and the second resistor, and the device is between the third resistor and the fourth resistor. 
     
     
         9 . The circuit of  claim 1 , wherein the first resistor comprises a first segment in the first direction and a second segment in the first direction, the first segment coupled to the second segment. 
     
     
         10 . A circuit comprising:
 a first resistor having a first terminal and a second terminal;   a second resistor having a first terminal and a second terminal, the first terminal coupled to the second terminal of the first resistor, wherein the second resistor is trimmable;   a third resistor having a first terminal and a second terminal, wherein the first terminal is coupled to the first terminal of the first resistor, wherein the third resistor is trimmable; and   a fourth resistor having a first terminal and a second terminal, wherein the first terminal is coupled to the second terminal of the third resistor and the second terminal is coupled to the second terminal of the second resistor.   
     
     
         11 . The circuit of  claim 10 , further comprising:
 an operational amplifier having a first input, a second input, and an output, the first input coupled to the second terminal of the third resistor and the second input coupled to the second terminal of the first resistor;   a third resistor having a first terminal and a second terminal, the first terminal coupled to the first input of the operational amplifier and the second terminal coupled to the output of the operational amplifier; and   a signal conditioner coupled to the output of the operational amplifier.   
     
     
         12 . The circuit of  claim 11 , further comprising a temperature sensor coupled to the signal conditioner. 
     
     
         13 . A circuit comprising:
 a first resistor configured to detect stress in a direction;   a second resistor, wherein the second resistor is trimmable; and   a compensation circuit coupled to the first resistor and to the second resistor, the compensation circuit configured to:
 obtain a resistance value based on the first resistor and the second resistor; and 
 produce a compensated signal based on the resistance value. 
   
     
     
         14 . The circuit of  claim 13 , wherein the compensation circuit comprises:
 an operational amplifier having an input and an output, the input coupled to at least one of the first resistor and the second resistor;   an analog circuit; and   a signal conditioner coupled to the output of the operational amplifier and to the analog circuit.   
     
     
         15 . The circuit of  claim 14 , wherein the signal conditioner is analog. 
     
     
         16 . The circuit of  claim 14 , wherein the signal conditioner is digital. 
     
     
         17 . The circuit of  claim 14 , wherein the signal conditioner is configured to transmit a compensated feedback signal to the analog circuit. 
     
     
         18 . The circuit of  claim 14 , further comprising:
 an operational amplifier having an input terminal and an output terminal;   a first transistor having a current terminal and a control terminal, the control terminal coupled to the output terminal of the operational amplifier, the current terminal coupled to the second resistor and to the input terminal of the operational amplifier; and   a second transistor having a current terminal and a control terminal, the control terminal coupled to the output terminal of the operational amplifier, and the current terminal coupled to the first resistor and to the compensation circuit.   
     
     
         19 . The circuit of  claim 13 , further comprising an operational amplifier having an input terminal and an output terminal, the input terminal coupled to the first resistor and to the second resistor, and the output terminal coupled to the compensation circuit. 
     
     
         20 . The circuit of  claim 13 , further comprising:
 a current source coupled to the first resistor;   an operational amplifier having a first input, a second input, and an output, the first input coupled to the first resistor, and the second input coupled to the second resistor;   a first transistor having a current terminal and a control terminal, the control terminal coupled to the output of the operational amplifier and the current terminal coupled to the input terminal of the operational amplifier; and   a second transistor having a current terminal and a control terminal, the control terminal coupled to the output of the operational amplifier and the current terminal coupled to the compensation circuit.